Vacuum tube device



g. 16, 1932. y|;\ ULREY VACUUM TUBE DEVICE Filed Nov. 5, 1925 INVENTOR Q//faf/ Z//r AT'TORNEY WITNESSES:

Patented Aug. 16, 1932 UNITED STATESV PATENT OFFICE TRIO & MANUFACTURING COMPANY, A

CORPORATION OF PENNSYLVANIA VACUUM TUBE DEVICE Application led November 5, 1925. Serial No. 66,879.

My invention relates to space current devices,'and particularly to vacuum tubes having a metal shell as an integral part of the container.

An object of my invention is to provide strengthening and protective means for the metal shell portion of a power vacuum tube.

Another object of my invention is to provide an electrodeposited protective covering upon the metal shell portion forming the external anode of a vacuum-tube device.

In prior art of vacuum tubes it has been customary to construct high-power vacuum tubes with a vapor tight metal shell portion, adapted to serve simultaneously as anode and having sealed thereto an insulating closure adapted to support other electrodes.

Diiculty has been encountered in the evacuation of such device because of an undue oxidation of the outer metal surface of the shell, during the baking out which is' incidental to the evacuation of the device and also because of the tendency of the thin metal shell to collapse by external pressure at the baking temperature.

My invention provides a strengthening and protecting means for the metal shell portion, which consists of an electrically deposited layer of another metal of greater strength and having greater resistance to oxidation.

Other objects and structural details of my invention will be apparent from the following description, when read in connection with the accompanying drawing, in which The single figure is a View in vertical elevation of a preferred embodiment of my invention. l

The vacuum-tube device of my invention consists of a metal shell portion 1, which may be of copper, and a glass portion 2 attached thereto by a seal 3. Suitable electrodes are ositioned within the shell portion 1 as shown y the dotted lines in the drawing. Upon the outer surface of the metal shell portion 1 is a coating 4 of a stronger, more resistant metal, which may be iron, or of iron with a coating of nickel thereover.

In the construction of my device, the metal shell portion 1 and the glass closure 2 are prepared in the usual way. The'seal between them is then produced in the customary manner by fusion to, and working over of the glass upon the edge of the metal shell l. The contained electrodes may be inserted at this point or may be inserted later in the usual way. The assembly comprising the metal shell 1, the glass portion 2 and the seal 3 may then be treated in an electro-deposition bath whereby a coating of electrically deposited iron 4 is caused to cover the metal shell portion 1 up to but not within or over the seal 3. Following the completion of the iron coating a second coating of nickel may be similarly added, `if desired.

In the operation of exhausting, the device, which may be placed in an oven in which a temperature in the neighborhood of 500 C. may be obtained, is connected by a pump leading to the evacuatingnsystem. Simultaneously, electrical connections are made to the filament and anode circuits in order that electron bombardment may be applied to the anode. The temperature of 500 C. is below that at which the glass portion of the device begins to soften, and therefore, the glass closure is not subject to destructive forces. The operation of electron bombardment, however, may raise the temperature of the metal shell portion, which-is the anode, to a temperature in the neighborhood of 800 C.

This temperature appears to be necessary in order to evolve all of the occluded gases but is above the temperature at which copper begins to lose its physical strength and, there fore, the copper shell would tend to collapse in the absence of the reinforcing coating 4. Also, the temperature is one which in the absence of the protecting coating 4 would be sufliciently high to cause the copper to tend toward rapid oxidation and thus remove metal from the thin portion near the seal to such an extent as may allow the copper shell to collapse at this point under the atmospheric pressure, or even cause an actual perforation because of removal of metal.

The presence of the electrically deposited coating of my invention however. counteracts this tendency. It furnishes suiicient additional strength to prevent thevcollapse of the copper and it furnishes suflicient resistanceto oxidation to prevent the removal of undesirable quantities of metal from the shell by oxidation and scaling.

By this means, I have produced a vacuumf tube device having much greater physical strength, which is much more resistant to corrosion and to pressure, and is much more convenient to manufacture.

While I haveshown but a single embodiment of my invention, it is capable of otherv changes and modifications therefrom and it coating, of another metal on said vapor-tight copper shell portion, said metal coating having greater resistance to oxidation than said copper. l

7. A vacuum tube device comprising a glass portion, a vapor-tight copper shell portion sealed thereto by means of a fused seal and acting as van exterior electrode, an interiorelectrode cooperating therewith and a coating of another metal on said vapor-ti ht copper shell portion, said metal coating belng of greater mechanical strength and havin is desired, therefore, that only such limita- `greater resistance to oxidation than sai tions shall be imposed thereon as are required by the prior art or indicated by the appended claims.

I claim as my invention:

1. The process of removing occluded gases from an outer metallic shell which acts as an electrode in a vacuum tube which comprises coating the yexterior of said shell with a second metal resistant to oxidation and then .heating said shell in an atmosphere containing oxygen to such a temperature that said metallic shell begins to lose its mechanical strength.

2. The process of removing occluded gases from an outer metallic shell which acts as an electrode in a vacuum tube which c`omprises coating the exterior of said shell with a second metal resistant to oxidation and then heating said shell in an atmosphere containing oxygen to a temperature in the neighborhood of 800 C.

3. The process of removing occluded gases from an outer copper shell which acts as an electrode in a vacuum tube which comprises DAYTON ULREY.

coating the exterior of .said shell with a sec- I ond metal resistantor oxidation and hen heating said shell in an atmosphere cont ining oxygen to a temperature in the neighborhood of 800 C.

4. The process of removing occluded gases from an outer metallic shell which acts as an electrode in a vacuum tube, the steps which comprise coating the exterior of said shell with a second metal having a higher melting point than has the material comprising said shell, and then heating said shell to such a temperature that said metallic shell begins to lose its mechanical strength.

5. A vacuum tube device comprising a glass portion, a vapor-tight copper shell portion sealed thereto by means of. a fused seal and acting as an exterior electrode, an interior electrode cooperating therewith and a coating of another metal on said vaportight copper shell portion, said metal coating being of greater mechanical strength than said copper.

6. A vacuum tube device comprising a glass portion, a vapor-tight copper shell portion sealed thereto by means of a fused seal and acting as an exterior electrode, an in- 65 terior electrode cooperating therewith and a 

